It is well know in the science of fluid mechanics that pipe elbows, valves and other physical disturbances in a fluid carrying conduit produce asymmetric changes in the fluid's velocity profile, eddy currents and other forms of fluid turbulence. Such disruptions in the laminar flow of the fluid are inconsistent with accurate flow rate measurement. Accordingly, without some kind of conditioning or straightening of the flow, a flow meter must be positioned a considerable distance from the element causing the turbulence. Often a straight run of pipe of up to ten pipe diameters is necessary before the fluid is in condition to be accurately measured for its flow rate.
Not surprisingly, this problem has seen the development of many types of apparatus to be placed downstream of a flow disturbing element to condition and straighten the fluid's flow before its contact with a flow meter. Such apparatus eliminates the need for multiple diameters of straight pipe upstream of a flow meter. Examples of such devices are seen in U.S. Pat. No. 3,733,898 for Flow Conditioning Apparatus, U.S. Pat. No. 5,596,152 for Flow Straightener for Turbine-Wheel Gasmeter, and U.S. Pat. No. 5,341,848 for Flow Conditioner, to name just a few. The problem with apparatus of the types disclosed in these and other patents is that they must be installed in the pipe line as an additional piece of equipment. Incident to such installation is initial cost, maintenance, pressure drop in the line and occupied space in the piping system.
In place of adding additional components into the pipe line it would be desirable to place the conditioning device in or combine it with the element that causes the problem in the first place. Accordingly, in view of this objective and because pipe elbows are the most frequent cause of laminar flow disturbance in fluid processing systems, it would be advantageous to provide a pipe elbow that not only serves its function of changing the direction of fluid flow, but at the same time maintains laminar flow.
It is therefore the primary object of the present invention to provide a pipe elbow that does not disturb the fluid passing through it so as to require subsequent flow conditioning.
A further object of the invention is to provide a pipe elbow whose configuration will condition flow disturbances that are created upstream of the elbow so that fluid exiting the elbow will be in proper condition for flow rate or other process measurement.
A still further object of the invention is to provide a fluid conditioning pipe elbow that will not produce a pressure drop in excess of that produced by a traditional pipe elbow.